Applying Textures

Applying Textures#

Download Python source code | Download Jupyter notebook

Plot a mesh with an image projected onto it as a texture.

from matplotlib.pyplot import get_cmap
import numpy as np
import pyvista as pv
from pyvista import examples

Texture mapping is easily implemented using PyVista. Many of the geometric objects come pre-loaded with texture coordinates, so quickly creating a surface and displaying an image is simply:

# load a sample texture
tex = examples.download_masonry_texture()

# create a surface to host this texture
surf = pv.Cylinder()

surf.plot(texture=tex)
texture

But what if your dataset doesn’t have texture coordinates? Then you can harness the pyvista.DataSetFilters.texture_map_to_plane() filter to properly map an image to a dataset’s surface. For example, let’s map that same image of bricks to a curvy surface:

# create a structured surface
x = np.arange(-10, 10, 0.25)
y = np.arange(-10, 10, 0.25)
x, y = np.meshgrid(x, y)
r = np.sqrt(x**2 + y**2)
z = np.sin(r)
curvsurf = pv.StructuredGrid(x, y, z)

# Map the curved surface to a plane - use best fitting plane
curvsurf.texture_map_to_plane(inplace=True)

curvsurf.plot(texture=tex)
texture

Display scalar data along with a texture by ensuring the interpolate_before_map setting is False and specifying both the texture and scalars arguments.

elevated = curvsurf.elevation()

elevated.plot(
    scalars='Elevation', cmap='terrain', texture=tex, interpolate_before_map=False
)
texture

Note that this process can be completed with any image texture.

# use the puppy image
tex = examples.download_puppy_texture()
curvsurf.plot(texture=tex)
texture

Textures From Files#

What about loading your own texture from an image? This is often most easily done using the pyvista.read_texture() function - simply pass an image file’s path, and this function with handle making a vtkTexture for you to use.

image_file = examples.mapfile
tex = pv.read_texture(image_file)
curvsurf.plot(texture=tex)
texture

NumPy Arrays as Textures#

Want to use a programmatically built image? pyvista.ImageData objects can be converted to textures using pyvista.image_to_texture() and 3D NumPy (X by Y by RGB) arrays can be converted to textures using pyvista.numpy_to_texture().

# create an image using numpy,
xx, yy = np.meshgrid(np.linspace(-200, 200, 20), np.linspace(-200, 200, 20))
A, b = 500, 100
zz = A * np.exp(-0.5 * ((xx / b) ** 2.0 + (yy / b) ** 2.0))

# Creating a custom RGB image
cmap = get_cmap('nipy_spectral')
norm = lambda x: (x - np.nanmin(x)) / (np.nanmax(x) - np.nanmin(x))
hue = norm(zz.ravel())
colors = (cmap(hue)[:, 0:3] * 255.0).astype(np.uint8)
image = colors.reshape((xx.shape[0], xx.shape[1], 3), order='F')

# Convert 3D numpy array to texture
tex = pv.numpy_to_texture(image)

# Render it
curvsurf.plot(texture=tex)
texture

Create a GIF Movie With Updating Textures#

Generate a moving gif from an active plotter with updating textures.

mesh = curvsurf.extract_surface(algorithm=None)

# Create a plotter object
pl = pv.Plotter(notebook=False, off_screen=True)

actor = pl.add_mesh(mesh, smooth_shading=True, color='white')

# Open a gif
pl.open_gif('texture.gif')

# Update Z and write a frame for each updated position
nframe = 15
for phase in np.linspace(0, 2 * np.pi, nframe + 1)[:nframe]:
    # create an image using numpy,
    z = np.sin(r + phase)
    mesh.points[:, -1] = z.ravel()

    # Creating a custom RGB image
    zz = A * np.exp(-0.5 * ((xx / b) ** 2.0 + (yy / b) ** 2.0))
    hue = norm(zz.ravel()) * 0.5 * (1.0 + np.sin(phase))
    colors = (cmap(hue)[:, 0:3] * 255.0).astype(np.uint8)
    image = colors.reshape((xx.shape[0], xx.shape[1], 3), order='F')

    # Convert 3D numpy array to texture
    actor.texture = pv.numpy_to_texture(image)

    # must update normals when smooth shading is enabled
    mesh.compute_normals(cell_normals=False, inplace=True)
    pl.write_frame()
    pl.clear()

# Closes and finalizes movie
pl.close()
texture

Textures With Transparency#

Textures can also specify per-pixel opacity values. The image must contain a fourth channel specifying the opacity value from 0 [transparent] to 255 [fully visible]. To enable this feature just pass the opacity array as the fourth channel of the image as a 3 dimensional matrix with shape [nrows, ncols, 4] pyvista.numpy_to_texture().

Here we can download an image that has an alpha channel:

rgba = examples.download_rgba_texture()
rgba.n_components

4

# Render it
curvsurf.plot(texture=rgba, show_grid=True)
texture

Repeating Textures#

What if you have a single texture that you’d like to repeat across a mesh? Simply define the texture coordinates for all nodes explicitly.

Here we create the texture coordinates to fill up the grid with several mappings of a single texture. In order to do this we must define texture coordinates outside of the typical (0, 1) range:

axial_num_puppies = 4
xc = np.linspace(0, axial_num_puppies, curvsurf.dimensions[0])
yc = np.linspace(0, axial_num_puppies, curvsurf.dimensions[1])

xxc, yyc = np.meshgrid(xc, yc)
puppy_coords = np.c_[yyc.ravel(), xxc.ravel()]

By defining texture coordinates that range (0, 4) on each axis, we will produce 4 repetitions of the same texture on this mesh.

Then we must associate those texture coordinates with the mesh through the pyvista.DataSet.active_texture_coordinates property.

curvsurf.active_texture_coordinates = puppy_coords

Now display all the puppies.

# use the puppy image
tex = examples.download_puppy_texture()
curvsurf.plot(texture=tex, cpos='xy')
texture

Spherical Texture Coordinates#

We have a built in convenience method for mapping textures to spherical coordinate systems much like the planar mapping demoed above.

mesh = pv.Sphere()
tex = examples.download_masonry_texture()

mesh.texture_map_to_sphere(inplace=True)
mesh.plot(texture=tex)
texture

The helper method above does not always produce the desired texture coordinates, so sometimes it must be done manually. Here is a great, user contributed example from this support issue

Manually create the texture coordinates for a globe map. First, we create the mesh that will be used as the globe. Note the start_theta for a slight overlap.

sphere = pv.Sphere(
    radius=1,
    theta_resolution=120,
    phi_resolution=120,
    start_theta=270.001,
    end_theta=270,
)

# Initialize the texture coordinates array
sphere.active_texture_coordinates = np.zeros((sphere.points.shape[0], 2))

# Populate by manually calculating
for i in range(sphere.points.shape[0]):
    sphere.active_texture_coordinates[i] = [
        0.5 + np.arctan2(-sphere.points[i, 0], sphere.points[i, 1]) / (2 * np.pi),
        0.5 + np.arcsin(sphere.points[i, 2]) / np.pi,
    ]

# And let's display it with a world map
tex = examples.load_globe_texture()
sphere.plot(texture=tex)
texture

Tags: plot

Total running time of the script: (0 minutes 5.417 seconds)

Gallery generated by Sphinx-Gallery